Method for preparing an insulating product based on wool, in particular mineral wool

ABSTRACT

A method for preparing an insulating product based on wool includes an aeration step inside a device, the device including a chamber and at least one structure capable of generating a turbulent gaseous flow, during the aeration step. A stream of carrier gas is introduced into the chamber and a wool in the form of nodules or flakes is subjected to the turbulent flow of this carrier gas with entrainment in one sense in a direction A and in the opposite sense in a direction B that is the opposite to the direction A so that within the chamber there is at least in one plane perpendicular to the direction A in which the wool entrained in the direction A crosses the wool entrained in the direction B.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.16/066,740, filed Jun. 28, 2018, pending, which is a 371 ofPCT/FR2016/053662, filed Dec. 23, 2016; the entire contents of each ofwhich are hereby incorporated by reference.

The invention relates to a method for preparing an insulating productcomprising wool, preferably mineral wool, to a device allowingpreparation of an insulating product, to an insulating product and to amethod of thermal insulation.

Mineral wool is a very good thermal and sound insulator because itcomprises entangled mineral fibers which give it a porous and elasticstructure. Such a structure allows air to be trapped and noise to beabsorbed or damped. Furthermore, mineral wool is manufacturedessentially from mineral materials, notably natural materials orrecycled products (recycled glass) and is thus attractive from anenvironmental balance standpoint. Finally, because mineral wool is basedon materials which are by nature non-combustible, it does not feed fireor spread flames. For preference, the mineral wool is selected fromglass wool and rock wool.

A distinction is made between, on the one hand, insulating products ofthe panel or roll type which come in the form of sheets or mats offibers, the cohesion of which is ensured by a binder (also referred toas size) which binds the fibers together by discrete point adhesion,and, on the other hand, products of the loose-fill type which take theform of small bundles of entangled fibers that form particles on acentimeter scale, in which no binding agent ensures the cohesion of thefibers in the bundles.

The manufacture of loose-fill mineral wool comprises at least thefollowing steps:

-   -   a step of melting the raw materials such as glass, in a melting        furnace,    -   a fiberizing step,    -   a step of forming a mat of mineral wool,    -   a step of nodulation using grinding.

The manufacture of loose-fill mineral wool may further comprise thefollowing steps:

-   -   a step of coating with agents such as antistatic agents and/or a        cohesion additive, prior to, at the same time as, or following        nodulation, and/or    -   a bagging step.

At the end of the nodulation step, the mineral wool is in the form ofnodules or flakes. The mineral wool may then be used as such as aloose-fill insulating product or as loose fill insulation, by spreadingit, blowing it, or filling cavities with it. A loose-fill insulationcorresponds, in the field of building, to a variety of materials offeredin the form of small particles the texture of which varies from granularto flake-like.

The mineral wool is advantageously used in the form of nodules or flakesas a main component in loose-fill insulation products for spaces thatare difficult to access such as the floors of roof spaces not suitablefor conversion which have not been developed or which are difficult toaccess.

These loose-fill insulating products are generally applied by mechanicalblowing using a blowing machine which allows an insulating product to besprayed over a surface or injected into a cavity from an outlet pipe.

These loose-fill insulating products are therefore mainly installed byspraying them directly into the space that is to be insulated, such asthe roof space, or by injecting them into a wall cavity.

Loose-fill insulating products are also referred to as blown insulation.

The insulating product once blown in needs to be as homogeneous aspossible to avoid thermal bridging and thus improve the thermalperformance. However, when the insulating product is blown in, whateverthe diameter of the outlet pipe, the mineral wool in the form of nodulesor flakes is not entirely homogeneous. The thermal conductivity of theresulting insulating product is not optimized.

A number of solutions have been considered for improving the homogeneityof loose-fill insulating products along their pneumatic journey.

Patent Applications EP1165998 and US 2006/0266429 disclose flexiblepipes which have mechanical means allowing the loose-fill insulation tobe expanded as it is being installed. These mechanical means areprojections extending over the internal surface of the pipes.

Application JP 2006/328609 discloses a complex method for expanding rockwool before storing it in a silo, comprising a step whereby agglomeratesof fibers are carried by a turbulent airflow qualified by a Reynoldsnumber of higher than 200000, inside a duct provided with several seriesof needles and of zones in relief so that the agglomerates collidingtherewith undergo mechanical opening.

These solutions, which are often excessively complex, are not entirelysatisfactory.

The applicant has developed a new preparation method that makes itpossible to obtain an insulating product comprising wool, preferablymineral wool, that has improved thermal performance.

The method of the invention for preparing a wool-based insulatingproduct comprises an aeration step inside a device comprising a chamberand at least one means capable of generating a turbulent gaseous flow.During this aeration step, a stream of carrier gas is introduced intothe chamber and a wool in the form of nodules or flakes is subjected tothe turbulent flow of this carrier gas with entrainment in one sense ina direction A, and in the opposite sense in a direction B that is theopposite to the direction A so that within the chamber there is at leastone plane perpendicular to the direction A in which the wool entrainedin the direction A crosses the wool entrained in the direction B.

The profile of the mean speeds of the mineral wool in the flow in thedirection A comprises at least one recirculation point or zone at whichthe component of speed parallel to the direction A is negative, makingit possible to generate the flow in the direction B. For preference,there are several recirculation points, so that one or morerecirculation loops or bubbles is formed in the flow.

It will be noted that the method of the invention uses a turbulent flowin the unsteady state. The explanations given in the present applicationwith regard to the speed profiles of the flows relate to thetime-averaged speeds averaged over a duration that is long in comparisonwith that of the fluctuations.

The wool is preferably a mineral wool, in particular chosen from glasswool or rock wool.

Glass wool is generally defined as being a product obtained from amolten mineral material derived from a mixture of vitrifiable rawmaterials and converted into a fiber by a method that is usuallycentrifugal spinning. Melting glass to a relatively viscous liquid formproduces fibers that are relatively long and fine.

Rock wool is generally defined as being a product obtained from a moltenmineral material derived from natural rocks and converted into a fiberby a method involving a series of rotating wheels. The melting ofnatural rock into the form of a highly fluid liquid produces fibers thatare relatively short and thick.

The aeration step significantly decreases the density of the wool,preferably mineral wool, in the form of nodules or flakes but above allhomogenizes the structure thereof. Surprisingly, the expansion and/orhomogenization of the wool subjected to the aeration step of theinvention is far better than that which can be obtained by the knownmethods of homogenization. The resulting insulating product can becompacted after the aeration step while maintaining a more homogeneousstructure.

The improvement in thermal performance is manifested in particular, inrelation to mineral wools not aerated according to the method of theinvention, in a reduction in the thermal conductivity for the samedensity or in a reduction in the density for the same thermalconductivity. The resulting insulating products also, for the samedensity, have a far higher airflow resistance.

The method of the invention makes it possible to expand the nodules orflakes so that it becomes practically impossible to determine theindividual dimensions thereof. That can be demonstrated by a simplevisual examination of the insulating products.

FIG. 1 comprises photographs respectively depicting:

FIG. 1 .A: a glass wool in the form of nodules or flakes that have notundergone the aeration step according to the invention and

FIG. 1 .B: a glass wool in the form of down having undergone theaeration step according to the invention.

FIG. 2 comprises photographs respectively depicting:

FIG. 2 .A: a rock wool in the form of nodules or flakes that has notundergone the aeration step according to the invention, and

FIG. 2 .B: an “expanded” rock wool in the form of nodules or flakeswhich has undergone the aeration step according to the invention.

The better homogeneity obtained by the method of the invention isclearly apparent from a simple visual examination of the insulatingproducts. Thus, a loose-fill mineral wool obtained according to theinvention adopts a novel form, that can be qualified as down, because itis very similar to animal down covering materials. What is thereforemeant by “down” in the present application is a loose-fill mineral woolin which the fibers that make up the mineral wool are almostindividualized, and the bundled structure of the flakes has beenpractically destroyed.

Although the method of the invention is quite particularly suitable formineral wools, in can be applied to any material that can be qualifiedas a “wool”, namely to any material made up of fibers positioned in anyway relative to one another and in the form of nodules or flakes.

The wool may be mineral or organic. A mineral wool comprises mineralfibers. An organic wool comprises organic fibers and may be chosen fromcotton wool, cellulose wadding wool, wood wool, hemp wool, flax wool,and recycled textile wool.

The invention also relates to a device allowing implementation of themethod of the invention. The device allows preparation of an insulatingproduct comprising wool. The device comprises a chamber (in which theaeration step is performed), means of introducing a wool in the form offlakes or nodules into the chamber, at least one means capable ofintroducing a turbulent gaseous flow into the chamber and of creatingwithin the chamber an entrainment of the wool in one sense in adirection A and in the opposite sense in a direction B that is theopposite to the direction A so that within the chamber there is at leastone plane perpendicular to the direction A in which the wool entrainedin the direction A crosses the wool entrained in the opposite sense inthe direction B.

The invention relates to the insulating product comprising wool,preferably mineral wool, that can be obtained by the method of theinvention.

Finally, the invention relates to a method of thermal insulation byspraying or blowing an insulating product directly into the space oronto the surface that is to be insulated or by injecting an insulatingproduct into a cavity, in particular a wall or partition wall cavity,using a device according to the invention.

The preferred features featured in the remainder of the description arejust as applicable to the preparation method according to the inventionas they are, where appropriate, to the insulating device, product ormethod.

A turbulent flow exhibits a range of speeds which fluctuate randomly intime and in space. These fluctuations are about a “mean” flowcorresponding to a mean over a duration that is long in comparison withthat of the fluctuations. According to the invention, what is meant by“turbulent flow” is a flow characterized by a Reynolds number higherthan 2000.

A turbulent flow can be defined by a mean speed. The mean speed of theturbulent flow carrying the wool in the direction A corresponds to theflow rate divided by the cross-sectional area of the chamber.

The chamber is configured in such a way that a turbulent set ofconditions capable of entraining the wool, preferably mineral wool, inthe carrier gas in the opposite sense in a direction B that is theopposite to the direction A becomes established from onwards of a pointqualified as the recirculation point. This recirculation point, when theprofile of the mean speeds in the flow in the direction A isrepresented, corresponds to a point at which the component of the speedparallel to the direction A acquires a negative value, thereby making itpossible to generate the flow in the direction B (from this point on).In FIG. 1 , A and B represent two speed vectors with the same directionand opposite sense. By convention, the speed along the vector A is saidto be positive and the speed along the vector B is said to be negative.

The recirculation points create instability which increases the level ofturbulence and creates the recirculation movements. Recirculation occursin a zone in which a quantity “q” of wool, preferably mineral wool,follows the flow in the direction B, namely flows countercurrent to thedirection A and follows a looped path.

The presence of recirculation points can be demonstrated by the presenceof recirculation bubbles corresponding to closed streamlines of mean(over time) speed. This is not seen in a conventional pneumaticconveyance means in which all of the material always advances in thesame mean sense.

A flow in the direction A comprising a recirculation point comprises ashear zone in which the wool travels in the direction A and arecirculation zone in which the wool travels in the direction B.

When representing the profile of the mean speeds in a plane of thechamber perpendicular to the direction A, a shear zone corresponds to avariation in the amplitude of the speed perpendicular to the directionA. Thus, when a flake of wool is situated in such a speed-variationzone, the material of which it is composed will be subjected locally todifferent entrainment speeds, thereby creating a shear effect.

The shear effect is further amplified if the variation in amplitude isaccompanied by a change in sense of the speed vector, as occurs in arecirculation zone. Shear is at a maximum at the recirculation point,which manifests itself as a zero speed changing sense at this point.Beyond the recirculation point, the wool, preferably mineral wool,therefore lies in the recirculation zone. When representing the profileof the speeds of the wool in the flow in the direction A, arecirculation zone is a zone at which the component of the speedparallel to the direction A is negative, something which ischaracteristic of flow in the opposite sense in the direction B, namelyentrainment of the mineral wool in the direction B that is the oppositeto the direction A.

The wool, preferably mineral wool, in the shear zone experiences highmechanical stresses which contribute to the “aerating” of the fibers.Passage through the recirculation zone makes it possible considerably tolengthen the time for which the mineral wool is subjected to high levelsof shear.

The turbulent flow in the direction A can easily be obtained byentraining the wool using a first air jet. This first air jet, whichpossibly contains wool in the form of flakes or nodules, enters thechamber from an inlet orifice. This inlet orifice may be an injectionnozzle, preferably cylindrical, or an end of an inlet pipe.

The turbulent flow in the direction A is preferably characterized by aReynolds number higher than 3000, preferably higher than 10000 andbetter still, higher than 100000. Because of the recirculation profileof the flow, there is no need for the turbulent nature to beparticularly pronounced. In this regard, it may seem preferable to keepa Reynolds number below 150000.

The first air jet enters the chamber from an inlet orifice. The flowfrom a first air jet at the level of the inlet orifice is characterizedby a Reynolds number higher than 3000, preferably higher than 10000, andbetter still, higher than 100000. A first air jet characterized by aReynolds number higher than 3000 allows the wool, preferably mineralwool, to be entrained and guarantees the turbulent nature of the flow.

The method of the invention, unlike the known systems, chiefly uses apneumatic or aeraulic system in which a gas, potentially compressed, isused as an aeration means in place of mechanical means in the form ofobstacles in the pneumatic conveyor. Any gas whatsoever may be suitable,with the exception of steam. For preference, the gas is air. The firstair jet may be created by a compressed-air source.

The method of the invention makes it possible to get around the problemof the wearing of mechanical means. But especially, the known methodsusing these mechanical means allow the insulating product to be expandedessentially by contact with the mechanical means.

According to the invention, the air jet allows the expansion orexpanding of any insulating product subjected to the air jet. As aresult, a greater quantity of insulating product can be expanded at thesame time. The use of turbulent flows according to the inventioncontributes to the obtaining of satisfactory speeds of expansion. Thespeed of expansion corresponds to the mass flow rate of insulatingproduct that can be obtained using the method of the invention.

There are several conceivable possible ways of generating arecirculation point that allows entrainment in a carrier gas in adirection B that is the opposite to the direction A.

According to a first embodiment, the entrainment in a carrier gas in adirection B that is the opposite to the direction A is obtained bychoosing suitable features:

for the first air jet, such as the dimensions of the cross section ofthe inlet orifice and the speed of the injected air, and

for the chamber, such as the shape and dimensions of said chamber.

The first air jet may be created by an air injector system equipped atits outlet with a nozzle, preferably cylindrical, opening into thechamber. The nodules or flakes present in the chamber are entrainedusing the first air jet and forms a turbulent flow in the direction A.

According to this embodiment, the cross section of the inlet orificecorresponding to the cross section of the injection nozzle needs to besmall enough in comparison with the cross section of the chamber for thefirst air jet to be comparable to a turbulent free jet in the “ambientair” of the chamber, which is assumed stationary. The jet is said to be“free” because no wall is supposed to perturb it.

At the “edges” of the jet, there is a high degree of shear (a hightangential stress due to the friction between the layers of fluid). Asthis high level of shear exists, not in the vicinity of a wall (as isthe case inside a cylindrical pipe) but in the vicinity of an immobilegas, the latter can very easily be set in motion. The ambient air isentrained to move, so vortexes are generated at the “edge” of the jet,at the boundary between it and the ambient air. These vortexes entrainwithin them wool, preferably mineral wool, in the form of nodules orflakes, in the direction B that is the opposite to the direction A.

At the edge of the jet, where the shear is strongest, the turbulent flowin the direction A comprises several recirculation points at which thecomponent of the speed parallel to the direction A is negative and thusallows the flow in the direction B to be generated.

According to this embodiment, the entrainment in a carrier gas in adirection B that is the opposite to the direction A is obtained bychoosing a suitable ratio between the dimensions of the cross section ofthe inlet orifice and a cross section of the chamber in a plane of thechamber perpendicular to the direction

A.

The chamber preferably comprises a cross section Se and a length L bothperpendicular to the direction A which are such that:

the dimensions of the cross section Se perpendicular to the direction Aare sufficient to generate a recirculation point in a plane of thechamber, and

the length L perpendicular to the direction A is short enough that therecirculation movements are multiplied.

According to this embodiment, the aeration step inside the chamber isperformed for a duration longer than 10 seconds, preferably 30 secondsand better still, 60 seconds.

According to another embodiment, the entrainment in a carrier gas in adirection B that is the opposite of the direction A is obtained by theuse of at least one additional air jet for which the direction in whichthe air is injected is at least partially the opposite to orperpendicular to the direction A.

The additional air jet or jets enter the chamber from inlet orifices,preferably injection nozzles. The flow from an additional air jet at thelevel of these inlet orifices is characterized by a Reynolds numberhigher than 3000, preferably higher than 10000, and better still, higherthan 100000.

In order to create a recirculation point through the use of additionalair jets, it is ideally necessary for the speed of the air leaving theadditional air jet to be higher than the mean speed of the flow carryingthe wool, preferably mineral wool. These jets generate a region ofrecirculation when the ratio of speeds between the additional air jetand the first jet exceeds a critical value.

According to this embodiment, the method meets one or more of thefollowing criteria:

-   -   the Reynolds number of the additional air jet is, in increasing        order of preference, higher then 3000, higher than 5000, higher        than 10000, higher than 10000, and/or    -   the Reynolds number of the additional air jet is higher than the        Reynolds number of the first air jet carrying the wool in the        direction A, and/or    -   the speed of the additional air jet is higher than the mean        speed of the turbulent flow carrying the wool in the direction        A, and/or    -   the ratio between the speed of the additional air jet and the        mean speed of the turbulent flow carrying the wool in the        direction A is greater than 1, preferably greater than 2, and        better still, greater than 4.

The mean speed of the turbulent flow which carries the wool, preferablymineral wool, in the direction A is comprised between 0.5 and 50 m/s. Inincreasing order of preference, the mean speed of the turbulent flowthat carries the wool, preferably mineral wool, in the direction A maybe comprised between 5 and 40 m/s or between 15 and 35 m/s, or between20 and 30 m/s, or between 25 and 30 m/s.

The insulating product is homogenized for long enough to allow theappearance of the nodules or flakes to be modified.

The chamber may be part of a duct or of a pipe. In that case, the meanspeed of the turbulent flow carrying the mineral wool is at least 10m/s, in particular at least 20 m/s or around 25 m/s. The part of thepipe that forms the chamber may be delimited by an inlet cross sectionwhich may comprise an inlet orifice possibly made in the solid wall, andan outlet cross section which may potentially comprise an outlet orificemade in a solid wall. The aeration zone thus adopts the form of achamber incorporated into the pipe, with a wall perpendicular to themain direction of the pipe. The aeration chamber may also consist of asimple section of tubular pipe the dimensions (cross section, length) ofwhich determine the formation of recirculation zones.

If the pipe is a blowing pipe, its length may be somewhere around 30 to50 m, the aeration chamber extending over all or part of the 30 to 50 m.If the length L of the chamber is 30 to 50 m, that means that a quantity“q” of mineral wool spends on average around 1 to 5 seconds in thechamber. When the chamber is part of a duct or of a pipe, the aerationstep in the chamber may be performed for a duration of a few seconds,for example more than 1 second, notably more than 3 seconds, for example5 seconds.

When the chamber forms part of a dedicated device, it may take the formof a chamber or silo with an entry lock, a confined space in which theaeration is performed, and an outlet lock provided with means ofopening/closing that can be controlled in accordance with a controlprogram that takes account of preset residence times. For example, inthe case of a dedicated chamber having a length of around 1 m, the timethat a quantity “q” of mineral wool spends there is around 200 ms. Theaeration step inside the chamber is performed for a duration in excessof 200 ms, preferably 0.5 s seconds and better, 1 second.

The aeration step may be performed at any time using a suitable device.

The aeration step may be performed during the manufacture of the wool,preferably mineral wool, in the form of nodules or flakes. In that case,the method for preparing the insulating product comprises at least thefollowing steps:

-   -   a step of melting the raw materials such as glass in a melting        furnace,    -   a fiberizing step,    -   a step of forming a mat of wool, preferably mineral wool,    -   a step of nodulation using grinding,    -   possibly a step of coating with agents such as antistatic agents        and/or a cohesion additive,    -   possibly a bagging step.

The aeration step may be performed after the step of nodulation bygrinding and before the bagging step. According to an alternative form,the aeration step may be performed after the bagging step.

When the bagging step is performed after the step of nodulation bygrinding before the bagging step, the pneumatic conveyor used to carrythe glass wool during manufacture may be fitted with a device foraerating the wool before the bagging step.

The aeration step may also be performed before or during the blowingstep.

Present-day mineral-wool-blowing machines comprise outlet pipespotentially fitted at their ends with a sleeve that may have an insidediameter that is smaller than the inside diameter of the outlet pipes.The geometry of the assembly constituted by the outlet pipe and thesleeve corresponds to a chamber exhibiting a convergent zone. The merepresence of a convergent zone in a chamber is not liable to createrecirculation points.

The Reynolds number that qualifies the flows in present-daymineral-wool-blowing machines is around 200000. The Reynolds number isbased on:

the diameter of the pipes, approximately 0.1 m,

the speed of spraying, approximately 20 m/s,

the kinematic viscosity, around 15.10⁻⁶ m²/s.

Present-day machines are unable to obtain a turbulent flow having arecirculation point that allows the air and mineral wool to recirculate.

The invention also relates to a device allowing preparation of aninsulating product comprising mineral wool. The device advantageouslycomprises a means for blowing the insulating product. In this case, thedevice is a blowing machine. The means for blowing the insulatingproduct comprise a pump and pipes.

Finally, the invention also relates to a thermal insulation method. Thespaces that are to be insulated are preferably the floors of roof spacesnot suitable for conversion, spaces behind or above suspended ceilings,or cavities of partition walls or hollow walls.

When the device further comprises a means for blowing the insulatingproduct, the method comprises a blowing step. The blowing step is thenperformed using a blowing machine. The mineral wool is expelled by anoutlet pipe using a pump or a turbine.

The aeration step may be performed during the blowing step by adaptingthe blowing machines. In that case, the turbulent flow can easily beobtained by entrainment of the mineral wool using an air jet. This airjet may be created by a compressed-air source potentially using the pumpof the blowing machine.

The insulating product according to the invention is essentially basedon expanded wool, preferably mineral wool. In the present description:

wool in the form of non-aerated nodules or flakes is the name given to awool that has not undergone an aeration step according to the invention,

wool in the form of down or wool in the form of expanded or aeratednodules or flakes is the name given to a wool that has undergone anaeration step according to the invention.

The mineral wool is chosen from glass wool and rock wool.

Nodules or flakes of mineral wool are fibers in bundles rather thanindividualized fibers like textile glass fibers. These nodules or flakesof mineral wool have a length comprised between 0.05 and 5 cm, inparticular between 0.1 and 1 cm. These flakes or nodules are formed offibers which are entangled in the form of small bundles, small rovings,or “pilling”. What is meant in the present description by the length ofthe flakes or nodules is the length of these bundles in their longestdimension.

Ideally, the mineral wool is expanded enough that the nodules and flakescan no longer be readily distinguished.

When the insulating product comprise glass wool, the flakes or nodulescan no longer be distinguished. The insulating product takes the form ofdown, namely of a product in the form of a layer of discontinuous fibersthat remain laid or grouped together in a form similar to a fibrous webin which the fibers are simply entangled (rather than bound) in a looseand fluffy structure. Portions of the down or of the web can be pickedup without the volumetric structure being affected.

The glass wool comprises glass fibers. Nodules or flakes of glass woolwhich are produced by the fiberizing of glass are described for examplein patent EP 2 511 586 by means of a device in particular comprising acentrifuge or centrifugal spinner and a basket. A stream of molten glassis fed to the centrifuge and flows out into the basket. The glass woolfibers are formed into nodules in the way explained in FR-A-2 661 687.These glass fibers are entangled.

Glass wool fibers differ from so-called “textile” glass fibers which areobtained by the high-speed mechanical drawing of the molten glass in theform of a sized filament.

The glass wool exhibits, in increasing order of preference, a micronairevalue:

-   -   less than 20 L/min, less than 15 L/min, less than 12 L/min, less        than 10 L/min,    -   greater than 2 L/min, greater than 3 L/min, greater than 4        L/min, greater than 5 L/min.

The micronaire value is measured in accordance with the method describedin document WO-A-03/098209.

The glass fibers of the glass wool are discontinuous. They have a meandiameter preferably less than 2 μm or even less than 1 μm.

The glass wool nodules or flakes are, for example, flakes made of glasswool of the type used for blown-wool insulation, for example of the typeof wools marketed by the Saint-Gobain Isover companies under thetradenames Comblissimo® or Kretsull® or by the

Certainteed company under the tradename Insulsafe®. These flakesgenerally have no binder and may contain anti-dust and/or antistaticadditives such as oils.

The rock wool comprises rock fibers. The rock wool has a fasonaire valueof at least 250. This parameter, which is also referred to as thefineness index, is measured in the way that is conventional in the fieldof rock wools. The fasonaire value is determined as follows: a testspecimen (5 g) made up of a tuft of mineral wool free of oil and binderbut which may contain non-fibrous components (nonfibers or “slugs” or“shots”) is weighed. This test specimen is compressed to a given volumeand has a stream of gas (dry air or nitrogen) kept at a constantflowrate passed through it. The fasonaire value measurement is then thedrop in pressure head through the test specimen, evaluated by a watercolumn graduated in conventional units. Conventionally, a fasonairevalue result is the mean of the drops in pressure head observed acrossten test specimens.

The insulating product comprises, in increasing order of preference, atleast 75%, at least 80%, at least 85%, at least 90%, at least 94%, atleast 95%, at least 96%, at least 97%, at least 98%, at least 99% wool,preferably mineral wool chosen from glass wool and rock wool, withrespect to the total mass of insulating product.

The insulating product comprises, in increasing order of preference, atleast 75%, at least 80%, at least 85%, at least 90%, at least 94%, atleast 95%, at least 96%, at least 97%, at least 98%, at least 99% ofmineral fibers, preferably glass fibers or rock fibers, with respect tothe total mass of insulation.

The insulating product comprises, in increasing order of preference, atleast 75%, at least 80%, at least 85%, at least 90%, at least 94%, atleast 95%, at least 96%, at least 97%, at least 98%, at least 99% ofmineral material, with respect to the total mass of insulating product.

EXAMPLES

A glass wool and rock wool, both in the form of non-aerated nodules orflakes, were used in these examples.

Before the aeration step, the glass wool is in the form of nodules or offlakes and comprises glass fibers with a micronaire value of 5.6 L/min.It exhibits a density of 11.6 kg/m³.

Before the aeration step, the rock wool is in the form of nodules or offlakes and comprises rock fibers with a fasonaire value of 250. Itexhibits a density of 74 kg/m³.

A device that makes it possible to perform the aeration step accordingto the invention is illustrated in FIG. 5 . This device comprises:

-   -   an air injection system 1 generating a first air jet,    -   a chamber 2,    -   an outlet opening 3.

The dimensions of this device are as follows: 30 cm×30 cm×40 cm with thelongest side situated in the direction of the jet.

For the glass wool, the first air jet is a “high-pressure” jet with aninlet pressure of around 4 bar.

For the rock wool, the first air jet is a jet obtained from a blowingmachine providing a sufficient inlet pressure.

The mineral wool in the form of nodules or flakes is introduced into thechamber 2. For example, approximately 100 g of glass wool are generallyintroduced. For rock wool, approximately the same quantity by volume isintroduced.

The mineral wool in the form of nodules or flakes is then subjected to aturbulent flow by being entrained in a carrier gas in a direction A withthe aid of a first high-pressure air jet generated by the air injectionsystem 1.

The mineral wool is subjected to a flow by entrainment in a carrier gasin a direction B that is the opposite to the direction A so that thereis, at least in one plane of the chamber perpendicular to the directionA, mineral wool entrained in the direction A and mineral wool entrainedin the direction B.

Entrainment in a carrier gas in a direction B that is opposite to thedirection A is the result of the choice of a suitable ratio between thecross section of the first jet and the size of the chamber. When theprofile of the mean speeds is represented, there is at least one (forpreference) several recirculation points in the chamber where thecomponent of the speed in the direction A is negative, which correspondsto a flow in the opposite sense in the direction B and thusrecirculation movements countercurrent to A.

This recirculation zone corresponds to a quantity “q” of mineral woolwhich at a given moment is going to go back in the countercurrent senseopposite to the direction A and pass the same point at least twice. Thestreamlines drawn in FIG. 5 suggest that a quantity of mineral woolperforms several loops passing through the same point several times.

The dimensions of the chamber are also tailored so that:

-   -   the dimensions perpendicular to the direction of the initial jet        are large enough to generate recirculation points in planes of        the chamber and    -   the dimension parallel to the direction of the jet is small        enough to multiply the recirculation movements.

When the mineral wool is sufficiently aerated, the insulating product isexpelled from the chamber through the outlet opening 3, either byactivation of an opening mechanism or because the chamber has been sizedso that the residence time between the mineral wool entering and theoutlet opening corresponds to the time needed to achieve the desireddegree of homogenization.

In this way there is obtained an insulating product according to theinvention comprising:

-   -   glass wool in the form of down, or    -   rock wool in the form of down or of expanded nodules or flakes.

This device allows 3 kg of insulating product based on glass wool to beaerated per hour.

The insulating products according to the invention after the aerationstep have low densities in particular of around 4 kg/m³ for productsbased on glass wool and around 50 kg/m³ for products based on rock wool.These products may if necessary undergo a compression step. Thecompression step may be performed by pressing the product between twoplates.

The ratio of the density prior to aeration to the density after aerationis preferably higher than 2, preferably higher than 2.5. Density is veryimportant in blow-in insulating products because it defines the coverageof the product corresponding to the area that can be covered with agiven mass of product to a defined depth.

1. Visual and Tomographic Observations

FIGS. 1 and 2 comprise photographs respectively depicting:

-   -   FIG. 1 .A: a glass wool in the form of nodules or flakes that        have not undergone the aeration step according to the invention,    -   FIG. 1 .B: an insulating product comprising loose-fill glass        wool in the form of down having undergone the aeration step        according to the invention,    -   FIG. 2 .A: a rock wool in the form of nodules or flakes that has        not undergone the aeration step according to the invention, and    -   FIG. 2 .B: an insulating product comprising “expanded” rock wool        in the form of nodules or flakes which has undergone the        aeration step according to the invention.

All the products according to the invention were obtained using thedevice of FIG. 5 .

These photographs show the better homogeneity of the insulating productsobtained according to the invention.

The tomography images in FIG. 3 respectively illustrate:

-   -   FIG. 3 .A: a glass wool in the form of nodules or flakes that        has not undergone the aeration step according to the invention,        exhibiting a density of 10 kg/m³,    -   FIG. 3 .B: an insulating product comprising loose-fill glass        wool in the form of down which has undergone the aeration step        according to the invention and exhibits a density of 4 kg/m³,    -   FIG. 3 .C: an insulating product comprising loose-fill glass        wool in the form of down having undergone the aeration step        according to the invention and a compacting step, and exhibiting        a density of 10 kg/m³.

The processing of these images is illustrated by the graphic in FIG. 4which represents the variations in terms of gray scale by volume. Theabscissa axis plots the intensity and the ordinate axis plots the numberof pixels exhibiting this intensity. A point on the curve corresponds tothe number of pixels found in the image at a given gray scale level.Curves (a), (b) and (c) respectively correspond to the insulatingproducts of FIGS. 3 .A, 3.B and 3.C.

These images and the processing of these images also show the betterhomogeneity of the insulating products according to the invention. Thatmanifests itself in a better distribution in terms of gray scale levels.The insulating products according to the invention have broader andnear-gaussian peaks, whereas the non-aerated glass wool has a narrowerand asymmetric distribution.

Finally, the insulating product that has undergone a compacting stepfollowing the aeration step, illustrated by image 3.C, maintains itsadvantageous properties in terms of homogeneity. It is thereforepossible thanks to the invention to obtain homogeneous insulatingproducts of variable densities.

2. Measuring the Thermal Conductivity and Airflow Resistance

The thermal conductivity measurements were taken in insulating products.The thermal conductivity A of a product is the ability of the product toallow a heat flux to pass though it; it is expressed in W/(m.K). Thelower this conductivity, the more insulating the product is, and thebetter the thermal insulation therefore is. The values of thermalconductivity as a function of density were measured in accordance withstandard EN14064.

Test specimens of the insulating product were conditioned to stabilizetheir weight at 23° C. for a relative humidity (RH) of around 50%. Themeasurements were taken at a mean temperature of 10° C. on an apparatusof R-Matic type on the cases of products measuring 590×590 mm, with athickness squashed down to a measured 108 mm. The actual measurementzone measures 254×254 mm. The mean thermal conductivity of theinsulating products is given in the table below.

The airflow resistance measurements in accordance with standard EN29053(method A) were taken on the same test specimens as were used formeasuring the thermal conductivity.

Several glass wools and one rock wool were used for these tests.

The thermal conductivity and airflow resistance of the test specimens ofinsulating products defined hereinafter were measured:

-   -   PI LVI NA: insulating product comprising glass wool, type 1,        non-aerated,    -   PI LVI A insulating product comprising glass wool, type 1,        aerated,    -   PI LV2 NA: insulating product comprising glass wool, type 2,        non-aerated,    -   PI LV2 A: insulating product comprising glass wool, type 2,        aerated,    -   PI LV3 A: insulating product comprising glass wool, type 3,        aerated,    -   PI LV4 A: insulating product comprising glass wool, type 4,        aerated,    -   PI LR NA: insulating product comprising rock wool, non-aerated,    -   PI LR A: insulating product comprising rock wool, aerated.

590 × 590 254 × 254 Rs density density Lambda Product (Pa · s/m²)(kg/m3) (kg/m3) (mW/(m · K) PI LV1 NA 590 9.3 9.6 50.7 — 9.5 9.6 48.9 PILV1 A 5762 10.2 10.2 36.8 4990 10.1 10.1 37.1 5988 10.0 10.0 39.4 603410.0 10.0 39.8 — 10.1 10.1 39.8 4990 9.9 9.9 40.4 4310 9.7 9.7 40.7 PILV2 NA 1642 11.6 11.6 46.0 PI LV2 A 1159 5.9 6.0 51.9 5070 11.5 12.937.2 PI LV3 A 628 4.1 4.1 59.3 5311 10.2 12.0 36.8 6132 10.1 11.5 37.1PI LV4 A — 10.1 9.8 39.8 6374 10.0 9.6 39.8 6422 10.0 9.9 39.4 5311 9.99.7 40.4 4587 9.7 9.8 40.7 435 2.9 3.0 78.9 44615 29.5 31.2 31.6 PI LRNA 5794 72.5 74.2 38.2 PI LR A 3525 39.1 43.0 39.1 18638 64.8 71.3 35.8

In terms of performance, the insulating products according to theinvention obtained after the aeration step have a thermal conductivitywhich is significantly lower.

The insulating products based on glass wool according to the inventionall have a thermal conductivity far below 42 mW·m⁻¹·K⁻¹ or even below 41mW·m⁻¹·K⁻¹ for densities comprised between 9.5 and 10.5 kg/m³.

An insulating product comprising aerated glass wool exhibits animprovement in thermal conductivity of more than 15%, preferably morethan 20%, by comparison with an insulating product comprisingnon-aerated glass wool for the same density. For a given performance,only half as much glass wool is needed in order to obtain the samethermal resistance.

Effectively, the glass wool in the form of non-aerated nodules or flakesexhibits, for a density of 10 kg/m³, a thermal conductivity of around 53mW·m⁻¹·K⁻¹.

The insulating product according to the invention exhibits, for the samedensity, a thermal conductivity of around 37 mW·m⁻¹·K⁻¹. Thatcorresponds to a reduction of 16 mW·m⁻¹·K⁻¹ and a 30% increase inthermal resistance for the same blown thickness.

The insulating product according to the invention exhibits, for the samethermal conductivity, a density of 4.8 kg/m³. That corresponds to areduction of 5.2 kg/m³, representing a material saving of 52%.

Alternative Forms of Embodiment

FIG. 6 illustrates three alternative forms of embodiment which maynotably be adapted to blowing machines.

Each of these devices comprises:

-   -   a chamber in which the aeration step is performed, and    -   at least one means capable of generating a turbulent flow within        the chamber.

The mineral wool in the form of nodules or flakes is subjected to aturbulent flow by entrainment in a carrier gas in a direction A using afirst high-pressure air jet. It arrives in the chamber 20 via a pipe 10at an inlet orifice 50. The recirculation may be generated byhigh-pressure jets 40 (FIGS. 6 .A and 6.C) and/or by adapting thegeometry of the device (FIGS. 6 .B and 6.C).

Each of these devices therefore comprises a means capable of generatinga flow by entrainment in a carrier gas in a direction B that is theopposite to the direction A so that there is, at least in one plane ofthe chamber perpendicular to the direction A, mineral wool entrained inthe direction A and mineral wool entrained in the direction B.

The devices 6.A and 6.C both comprise additional air jets 40 of whichthe direction of spraying in a plane of the chamber perpendicular to thedirection A is at least in part the opposite of the direction A. This orthese additional air jets enter the chamber from injection nozzles,preferably cylindrical.

The devices 6.B and 6.C both comprise a chamber having dimensions and across section for the inlet orifice 50 that allow and/or contribute tothe entrainment in a carrier gas in a direction B that is the oppositeto the direction A. The ratio between the cross section of the inletorifice 50 and a cross section of the chamber in a plane of the chamberperpendicular to the direction A is adapted so as to generaterecirculation points.

The insulating product according to the invention emerges via an outletpipe 30.

FIG. 7 illustrates an alternative form of embodiment that can be adaptedto any pipe or duct and, in particular:

-   -   to a conveying pipe used to carry mineral wool in the form of        flakes or nodules, for example at a factory,    -   to a pipe of a blowing machine.

This device comprises a high-pressure air jet ring on the passage of theglass wool. FIG. 7 illustrates part of a pipe or duct that acts as achamber comprising an inlet 100, an outlet 300 and several additionalair jets the inlet orifices 400 of which are situated directly on partof the pipe. The air of the additional jets is preferably injected athigh pressure.

This device comprises additional air jets 400 of which the direction ofspraying in a plane of the chamber perpendicular to the direction A isperpendicular to the direction A. This or these additional air jetsenter the chamber from injection nozzles, preferably cylindrical.

FIG. 8 illustrates another alternative form of embodiment comparablewith a fluidized bed. This device comprises a means of admitting mineralwool in the form of nodules or flakes 100, a chamber in which theaeration step takes place 200, an insulating product outlet means 300,an air inlet 500 and an air outlet 600. It is possible to improve theturbulent conditions or to optimize the time spent in the chamber by theaddition of air inlets such as air jets or mechanical obstacles in thechamber 200. This device can easily be added to a mineral woolmanufacturing line. It could for example be coupled to another pneumaticsystem, in particular prior to a step of separating air and fibers.

1: A method for preparing an insulating product based on wool,comprising: an aeration step inside a device, the device comprises achamber and at least one means capable of generating a turbulent gaseousflow, during the aeration step, a stream of carrier gas is introducedinto the chamber and a wool in the form of nodules or flakes issubjected to the turbulent flow of the carrier gas with entrainment in adirection A and in a direction B that is the opposite to the direction Aso that within the chamber there is at least in one plane perpendicularto the direction A in which the wool entrained in the direction Acrosses the wool entrained in the direction B. 2: The method forpreparing an insulating product as claimed in claim 1, wherein the woolis a mineral wool. 3: The method for preparing an insulating product asclaimed in claim 1, wherein the profile of the mean speeds of the woolin the flow in the direction A comprises at least one recirculation zonein which the component of the speed parallel to the direction A isnegative, thereby making it possible to generate the flow in thedirection B. 4: The method for preparing an insulating product asclaimed in claim 3, wherein the flow in the direction A comprising arecirculation point comprises a shear zone in which the wool travels inthe direction A and a recirculation zone in which the wool travels inthe direction B. 5: The method for preparing an insulating product asclaimed in claim 1, wherein the turbulent flow in the direction A ischaracterized by a Reynolds number higher than
 3000. 6: The method forpreparing an insulating product as claimed in claim 1, wherein theturbulent flow in the direction A is obtained by entraining the woolusing a first air jet. 7: The method for preparing an insulating productas claimed in claim 6, wherein the first air jet enters the chamber froman inlet orifice, the flow of the first air jet at the level of theinlet orifice is characterized by a Reynolds number higher than
 3000. 8:The method for preparing an insulating product as claimed in claim 6,wherein the entrainment in a carrier gas in a direction B that is theopposite to the direction A is obtained by choosing a suitable ratiobetween the dimensions of the cross section of the inlet orifice and across section of the chamber in a plane of the chamber perpendicular tothe direction A. 9: The method for preparing an insulating product asclaimed in claim 1, wherein the chamber comprises a cross section Se anda length L both perpendicular to the direction A which are such that thedimensions of the cross section Se perpendicular to the direction A aresufficient to generate a recirculation point in a plane of the chamber,and the length L is short enough that the recirculation movements aremultiplied. 10: The method for preparing an insulating product asclaimed in claim 8, wherein the aeration step inside the chamber isperformed for a duration longer than 10 seconds. 11: The method forpreparing an insulating product as claimed in claim 1, wherein theentrainment in a carrier gas in a direction B that is the opposite tothe direction A is obtained by the use of at least one additional airjet for which the direction in which the air is injected is at leastpartially the opposite of (in the opposite direction to) orperpendicular to the direction A. 12: The method for preparing aninsulating product as claimed in claim 11, wherein the additional airjet or jets enter the chamber from inlet orifices, the flow from anadditional air jet at the level of these inlet orifices is characterizedby a Reynolds number higher than
 3000. 13: The method for preparing aninsulating product as claimed in claim 12, wherein the Reynolds numberof the additional air jet is higher than the Reynolds number of thefirst air jet which carries the wool in the direction A. 14: The methodfor preparing an insulating product as claimed in claim 11, wherein thespeed of the additional air jet is higher than the mean speed of theturbulent flow that carries the wool in the direction A. 15: The methodfor preparing an insulating product as claimed in claim 11, wherein theratio between the speed of the additional air jet and the mean speed ofthe turbulent flow that carries the wool in the direction A is greaterthan
 1. 16: The method for preparing an insulating product as claimed inclaim 1, wherein the mean speed of the turbulent flow which carries thewool in the direction A is comprised between 0.5 and 50 m/s. 17: Themethod for preparing an insulating product as claimed in claim 1,wherein the chamber is part of a duct or of a pipe. 18: The method forpreparing an insulating product as claimed in claim 1, furthercomprising at least the following steps: a step of melting the rawmaterials such as glass, in a melting furnace, a fiberizing step, a stepof forming a mat of wool, preferably mineral wool, a step of nodulationusing grinding, a step of coating with agents such as antistatic agentsand/or a cohesion additive, a bagging step. 19: The method for preparingan insulating product as claimed in claim 18, wherein the aeration stepis performed after the step of nodulation by grinding and before thebagging step. 20: The method for preparing an insulating product asclaimed in claim 18, wherein the aeration step is performed after thebagging step.